kernel/trace/trace_kdb.c

   1 /*
   2  * kdb helper for dumping the ftrace buffer
   3  *
   4  * Copyright (C) 2010 Jason Wessel <jason.wessel@windriver.com>
   5  *
   6  * ftrace_dump_buf based on ftrace_dump:
   7  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   8  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   9  *
  10  */
  11 #include <linux/init.h>
  12 #include <linux/kgdb.h>
  13 #include <linux/kdb.h>
  14 #include <linux/ftrace.h>
  15
  16 #include "../debug/kdb/kdb_private.h"
  17 #include "trace.h"
  18 #include "trace_output.h"
  19
  20 static void ftrace_dump_buf(int skip_lines, long cpu_file)
  21 {
  22         /* use static because iter can be a bit big for the stack */
  23         static struct trace_iterator iter;
  24         unsigned int old_userobj;
  25         int cnt = 0, cpu;
  26
  27         trace_init_global_iter(&iter);
  28
  29         for_each_tracing_cpu(cpu) {
  30                 atomic_inc(&iter.tr->data[cpu]->disabled);
  31         }
  32
  33         old_userobj = trace_flags;
  34
  35         /* don't look at user memory in panic mode */
  36         trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  37
  38         kdb_printf("Dumping ftrace buffer:\n");
  39
  40         /* reset all but tr, trace, and overruns */
  41         memset(&iter.seq, 0,
  42                    sizeof(struct trace_iterator) -
  43                    offsetof(struct trace_iterator, seq));
  44         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  45         iter.pos = -1;
  46
  47         if (cpu_file == TRACE_PIPE_ALL_CPU) {
  48                 for_each_tracing_cpu(cpu) {
  49                         iter.buffer_iter[cpu] =
  50                         ring_buffer_read_prepare(iter.tr->buffer, cpu);
  51                         ring_buffer_read_start(iter.buffer_iter[cpu]);
  52                         tracing_iter_reset(&iter, cpu);
  53                 }
  54         } else {
  55                 iter.cpu_file = cpu_file;
  56                 iter.buffer_iter[cpu_file] =
  57                         ring_buffer_read_prepare(iter.tr->buffer, cpu_file);
  58                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  59                 tracing_iter_reset(&iter, cpu_file);
  60         }
  61         if (!trace_empty(&iter))
  62                 trace_find_next_entry_inc(&iter);
  63         while (!trace_empty(&iter)) {
  64                 if (!cnt)
  65                         kdb_printf("---------------------------------\n");
  66                 cnt++;
  67
  68                 if (trace_find_next_entry_inc(&iter) != NULL && !skip_lines)
  69                         print_trace_line(&iter);
  70                 if (!skip_lines)
  71                         trace_printk_seq(&iter.seq);
  72                 else
  73                         skip_lines--;
  74                 if (KDB_FLAG(CMD_INTERRUPT))
  75                         goto out;
  76         }
  77
  78         if (!cnt)
  79                 kdb_printf("   (ftrace buffer empty)\n");
  80         else
  81                 kdb_printf("---------------------------------\n");
  82
  83 out:
  84         trace_flags = old_userobj;
  85
  86         for_each_tracing_cpu(cpu) {
  87                 atomic_dec(&iter.tr->data[cpu]->disabled);
  88         }
  89
  90         for_each_tracing_cpu(cpu)
  91                 if (iter.buffer_iter[cpu])
  92                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  93 }
  94
  95 /*
  96  * kdb_ftdump - Dump the ftrace log buffer
  97  */
  98 static int kdb_ftdump(int argc, const char **argv)
  99 {
 100         int skip_lines = 0;
 101         long cpu_file;
 102         char *cp;
 103
 104         if (argc > 2)
 105                 return KDB_ARGCOUNT;
 106
 107         if (argc) {
 108                 skip_lines = simple_strtol(argv[1], &cp, 0);
 109                 if (*cp)
 110                         skip_lines = 0;
 111         }
 112
 113         if (argc == 2) {
 114                 cpu_file = simple_strtol(argv[2], &cp, 0);
 115                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 116                     !cpu_online(cpu_file))
 117                         return KDB_BADINT;
 118         } else {
 119                 cpu_file = TRACE_PIPE_ALL_CPU;
 120         }
 121
 122         kdb_trap_printk++;
 123         ftrace_dump_buf(skip_lines, cpu_file);
 124         kdb_trap_printk--;
 125
 126         return 0;
 127 }
 128
 129 static __init int kdb_ftrace_register(void)
 130 {
 131         kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
 132                             "Dump ftrace log", 0, KDB_REPEAT_NONE);
 133         return 0;
 134 }
 135
 136 late_initcall(kdb_ftrace_register);